Electric discharge lamp



Jam 3L 195o F T, OHEARN 2,496,065

ELECTRIC DISCHARGE-LAMP Filed Jan. 16. 1948 2 no wem/www INVENTOR.

FRANcBll/s T.'VOHEARN l GM/N/vvuy [6MM] Afro QNEY M M H 8 Patented Jan. 3l, 1950 ELECTRIC DISCHARGE LAMP Francis T. OHearn, Sylvania Electric Lowell, Mass., asslgnor to Products Inc., Salem,

Mass.,

a corporation of Massachusetts Application January 16, 1948, Serial No. 2,632 2 Claims. (Cl. 176-122) This invention relates to electric discharge devices in general and in particular to such devices in which the discharge produces ultraviolet radiations.

Such devices are generally enclosed in an envelope of glass, quartz or the like, which is blackened or otherwise diminished in its ultraviolet or visible transparency during life by the action of the discharge, especially when mercury vapor is present in the lamp. This action is particularly rapid when the device is operated in ambient temperatures near, at or below freezing, such as the ambient temperature of a refrigerator in which ultraviolet lamps may be used for their germicidal effect.

A feature of the invention is an auxiliary electrode of zirconium metal in close proximity to a thermionic electrode.

Other features, advantages and objects of the invention will be apparent from the following. specification, taken in connection with the accompanying specication, in which:

Figure 1 is a partly sectional view of a device according to the invention; and

Figure 2 is a view of the electrode structure of said device in more detail.

In Figure 1, the tubular glass envelope l is sealed at both ends to stems such as 2, through which lead-in wires 3, 4 extend to support a thermionic electrode 5, which may comprise a coiled coil of tungsten wire, coated for example with one or more of the alkaline earth oxides in the usual manner to secure copious electron emission, for example as described in Lowry Patent 2,258,158, issued October 7, 1941. The lamp is filled with an inert gas at low pressure, say argon at 3 mm. of mercury pressure, for example, and contains a small quantity of mercury to insure the presence of mercury vapor during operation of the device. A base 6 is cemented or otherwise attached to each end of the lamp, and carries the contact pins l, 8 attached respectively to lead-in wires 3, 4 for electrical contact. The base 6 terial, at least in the vicinity of the pins 1, 8 to insulate the saine. If the lamp is to emit ultraviolet radiations the envelope i should be of a material pervious thereto, for example a substantially iron-free borosilicate glass.

The zirconium metal auxiliary electrode i0. preferably comprises a wire l2, extending parallel to the main longitudinal axis of the electrode coil and connected to the lead-in wire This wire i2 will act as an anode during alternate half cycles, if the lamp is operated on alternating current, and will consequently become heated, thereby increasing the edectiveness of the ziris of insulating mal` main electrode of the Per cent of Initial Output 0 Hours 100 Hours 300 Hours 500 Hours No Zirconlum 6l. 4 44. 6 33. 7 0.01 inch Zirconlum 100 73. l 66. 2 57. 8

'I'he above was for a single 9 mm. long zirconium auxiliary electrode at each main electrode, with a lamp current of 300 mllliamperes, and a type shown in Lowry Patent 2,258,158. The eil'ectiveness of the zirconium is obvious; it nearly doubled the output at 500 hours.

What I claim is:

1. An electric gaseous discharge device comprising an envelope, a gas filling therein, a pair of electrodes therein, a coating of an oxide of an alkaline earth metal on each of said electrodes, and a pair of zirconium metal auxiliary elec-i trodes, each of said auxiliary electrodes being spaced from one of said coated electrodes but in close proximity thereto and connected to one end thereof.

2. An electric gaseous discharge device comprising an envelope of substantially iron-free borosilicate glass, a filling oi' inert gas at low pressure therein, a small quantity of mercury therein, a pair of coiled wire electrodes therein, a coating of an oxide of at least one of the alkaline earth metals on each of said electrodes, and a pair of zirconium metal auxiliary electrodes, each of said auxiliary electrodes being electrically connected to one end of each of said coiled wire electrodes and extending parallel and in close proximity thereto, but spaced therefrom.

FRANCIS T. OHEARN REFERENCES CITED The following references are of record in the file of this patent: f

STATES PATENTS 

